1. Field of the Invention
The invention is directed to a microscope in which a specimen is arranged between two objectives and can be observed with reflected light as well as with transmitted light.
2. Description of the Related Art
An important concern in further developments in microscopy at present is to provide and perfect methods and arrangements which make it possible to observe objects by twofold transmission with reflected light as well as with transmitted light, which serves to increase both resolving capacity and contrast.
In this regard, there are already known arrangements in which incident light transmitted by the object is reflected back to the rear of the object again by a reflecting device. The invention described in the following also belongs to this class of arrangement.
An early solution using a reflecting device for the light transmitted by the object is described in DE 10 83 065. In this case, there is provided in the beam path behind the object a multiple corner reflector or triple mirror which depolarizes the polarized light of the vertical or incident illumination and cooperates with a crossed analyzer arranged in the observation beam path in such a way that only the depolarized beam component proceeding from the triple mirror can pass the analyzer and thus result in a transmitted-light image of the object illuminated by incident light.
However, because of the influence of image errors (aberrations, etc.) and alignment or adjustment inaccuracies, the image of the object to be observed has relatively weak lighting and poor contrast.
A further development in this respect according to DE 32 04 686 A1 provides an optical system for transmitted-light microscopy with vertical or incident illumination in which it is attempted by means of a specially constructed reflecting device to allow light beams which pass through the object and are then reflected upon the object again to pass identical object points in both directions. For this purpose, it is suggested that, for example, an autocollimation system with optics which image the back of the object onto a plane mirror and image the occurring image on the underside of the object is used as a reflecting device. An improved contrast enhancement can be achieved with this system and the arrangement developed from it. In order to prevent aperture losses, the autocollimation system comprises, for example, two objectives with infinite output back focal distance or output intersection length, wherein the object plane and the surface of the plane mirror lie in the focal point of the two objectives.
However, the reflection carried out in this manner also has alignment inaccuracies and image errors, as a result of which the light is not exactly parallel after the second objective or the object to be observed is not imaged onto itself with lateral and vertical precision.